Hardening medium and process for hardening tools of iron or steel



MM 1....3, 1933 I 1,893,077

UNITED STATES PATENT OFFICE AUGUST GABWEG, OF 'WUPPEB'I'AL-BONSDOBF,GERMANY EARDENHIG MEDIUM AND PROCESS FOR HABDENING TOOLS OF IRON ORSTEEL Ho Drawing. Application filed September 28, 1881, Serial No.565,399, and in Germany September 26, 1930.

This invention relates to a hardening memixture composed of a very smallquantity dium and a process for hardening tools of of water, 250 grs ofcarbon dust, 7 grs of iron or steel, especially such which come intopotassium-ferro-cyanide, ltr of oil and question for the working ofwood, cardboard, 250 grs of ground slate.

5 leather and the like. In testimony whereof I afiix my signature.

The new hardening medium difiers from the known media in that to amixture of AUGUST'GARWEG. water, carbon dust, potassium-ferro-cyanideand oil pulverized argillaceous slate is added in such a manner that 250grs of ground slate are added to a mixture composed of a very smallquantity of water, 250 grs of carbon dust, 75 grs ofpotassium-ferro-cyanide and ltr of oil.

The new process consists in that by employin the above mentionedhardening medium ac tool heated to 600 to 700? C. is strewn withpotassium-ferro-cyanide, is again heated to 800 to 900 C. after thissalt 20 has penetrated in the tool and the tool is then 7c 1 cooled in amixture'composed of one art by weight of water, 250 grs of carbon dhst,7 5 grs of potassium-ferro-cyanide, ltr of oil and 250 grs of oundslate.

Care must taken that the potassium- 5 ferro-cyanide has thorou hlypenetrated before the second heating 0 the tool. It is advisable aftercooling the tool in the above mentioned mixture to again dip same incold water.. 3

This manner of treatment of tools made of iron or steel causes arefining and a cut resistin hardness in the critical zones of thematerial, thereby preventing the occurrence of cracks or crevices.

I claim 1. A hardening medium for tools made of iron and steel,comprising a mixture of a very 40 small quantity of water, 250 grs ofcarbon dust, 7 5 grs of potassium-ferro-cyanide and ltr of oil to which250 grs of ground slate are added. 4

2. A method for hardenin tools of iron and steel em loying the bar eningmedium specified in c aim 1, consisting in heating the tool to 600 to700 0., in strewing potassiumferro-cyanide on the tool thus heated, inagain heating the tool to 800 to 900 C. after thepotassium-ferro-cyanide has penetrated therein, and in finally coolingthe tool in a

